demo-video

Demo Video Assembly Skill

This skill assembles a narrated demo video from ordered visual segments and matching narration audio. It is designed for first-pass walkthrough videos that combine captured prototype frames or clips with per-segment voiceover WAV files.

Overview

The workflow takes a manifest that describes each segment, resolves the visual source, and uses FFmpeg to render each segment into a normalized video clip before concatenating them into a final MP4. The narration track is muxed from WAV files so the output can be reviewed as a polished walkthrough without requiring a separate video-editing tool.

Manifest Schema

Use a segments.yml manifest with optional top-level output settings and an ordered list of segments. Each entry describes a visual source and the narration audio to combine for that portion of the video. All paths resolve relative to the manifest file.

output: ./output/demo.mp4   # optional; destination path for the assembled MP4
resolution: 1280x720        # optional; default 1280x720
fps: 24                     # optional; default 24
segments:
  - type: frame
    visual: ./frames/intro.png
    narration: ./audio/intro.wav
    duration: 4.5
  - type: clip
    clip: ./clips/interaction.mp4
    narration: ./audio/interaction.wav

Top-level fields

• output sets the destination path for the assembled MP4, resolved relative to the manifest; the --output or -OutputPath argument overrides it when supplied
• resolution controls the output width and height in WIDTHxHEIGHT form (default 1280x720); the --resolution or -Resolution argument overrides it
• fps sets the frame rate applied when rendering each segment (default 24); the --fps or -Fps argument overrides it

Segment fields

• type identifies whether the segment is a still image (frame) or a motion clip (clip)
• visual points to an image file for a frame segment
• clip points to a motion clip file for a clip segment
• narration points to the WAV file generated from narration text (the script also accepts narration_wav as an alias)
• duration is optional and overrides the inferred duration when you want a fixed segment length